CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ACCUMULATED OTHER COMPREHENSIVE LOSS	ADDITIONAL PAID-IN CAPITAL	RETAINED EARNINGS
Balance at beginning of period at Dec. 31, 2014		$ 569	$ (2,017)	$ 16,324	$ 147
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2		9
Repurchase of common stock		(17)		(518)
Shares withheld to satisfy tax withholdings				(18)
Share-based compensation and other, net				58
Dividends declared				(395)	(510)
Other comprehensive income	$ 76		76
Net income	540				540
Balance at end of period at Sep. 30, 2015	14,250	554	(1,941)	15,460	177
Balance at beginning of period at Dec. 31, 2015	14,060	544	(1,934)	15,178	272
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		3		5
Repurchase of common stock		0		0
Shares withheld to satisfy tax withholdings				(15)
Share-based compensation and other, net				59
Dividends declared				(106)	(777)
Other comprehensive income	79		79
Net income	584				584
Balance at end of period at Sep. 30, 2016	$ 13,892	$ 547	$ (1,855)	$ 15,121	$ 79